document.getElementById("submit").onclick = function(){
    var ok = true;
    if(trim(document.getElementById("Name").value) != ''){
        document.getElementById("nameErr").innerHTML = '';
    }else{    
        document.getElementById("nameErr").innerHTML = 'Please enter your name.';
        ok = false;        
    }
    emailfilter = /^(("[\w-\s]+")|([\w-]+(?:\.[\w-]+)*)|("[\w-\s]+")([\w-]+(?:\.[\w-]+)*))(@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$)|(@\[?((25[0-5]\.|2[0-4][0-9]\.|1[0-9]{2}\.|[0-9]{1,2}\.))((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\.){2}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[0-9]{1,2})\]?$)/i
    if(emailfilter.test(document.getElementById("Email").value)){
        document.getElementById("emailErr").innerHTML = '';
    }else{    
        document.getElementById("emailErr").innerHTML = 'Please enter a valid email.';
        ok = false;
    }
    var skill = false;
    for(var i = 0; i < document.getElementById("Skill").options.length; i++){
        if(document.getElementById("Skill").options[i].selected){
            skill = true; 
            break;
        }
    }
    if(skill){
        document.getElementById("skillErr").innerHTML = '';
    }else{    
        document.getElementById("skillErr").innerHTML = 'Please select at least one skill.';
        ok = false;
    }
    if(trim(document.getElementById("Message").value) != ''){
        document.getElementById("messageErr").innerHTML = '';
    }else{    
        document.getElementById("messageErr").innerHTML = 'Please enter a message.';
        ok = false;
    }
    if(ok){
        alert("Thank you for joining our team, A response will be send as soon as possible.");
    }
    return ok;
}

function trim(value) {
  value = value.replace(/^\s+/,''); 
  value = value.replace(/\s+$/,'');
  return value;
}